Low-Energy Excitations in (KBr)1−x(KCN)x in the Orientational Glass State
CN− ions substituting in small concentrations for Br− ions in KBr are known to possess low energy, quasirotational tunneling and librational states. For molar concentrations x>0.01, (KBr)1−x(KCN)x is believed to enter into a quadrupolar glass phase at low temperature [1,2]. We have measured the low-temperature thermal conductivity and specific heat of this mixed crystal system for x=0.25 and 0.5, and have found it to possess the same low-energy excitations as are seen in amorphous solids.
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